1. Field of the Invention
The present is related to phacoemulsification needles or cannulas for use in ophthalmic surgery, especially cataract surgery. More particularly, the present invention is directed to a phacoemulsification cannula with improved purchase or suction at the distal end of the cannula.
2. Description of Related Art
The use of phacoemulsification cannulas in ophthalmic surgery and especially in cataract surgery is well known. Typical cannulas include an inner lumen through which fluids and tissue are aspirated away from a patient's eye, through the lumen of the aspiration needle, and eventually to a collection bag or cassette. The purpose of the phacoemulsification cannula is to transfer ultrasonic energy from a phacoemulsification handpiece in order to break-up cataracts in the eye and then aspirate fluids and the cataract tissue through the lumen of the cannula.
There have been many phacoemulsification cannula designs which typically are directed towards improving the break-up of cataract tissue in order to make the surgery more time efficient. Such designs include having angled tips and having bores within the tip that transition from a larger diameter to a smaller diameter. In addition, these larger bores at the distal end of the phacoemulsification needles typically are either stepped in their transition or tapered. Each of these prior art needles or cannulas has been designed to more efficiently break-up cataract tissue once it has been sucked within the cannula lumen. Because of the longitudinal in and out or jack hammer-like motion of the phaco needle during the use of ultrasonic energy, it is often difficult for the phacoemulsification cannula to make significant contact with the cataract. This is because as the cannula moves out away from the handpiece and towards the cataract, the cannula effectively pushes the cataract away. A surgeon relies on the vacuum or suction force of the surgical system that is asserted through the lumen of the cannula to hold or purchase the cataract to the cannula. In order to provide greater purchase of the cannula, the aspiration levels need to be increased. Such an increase in aspiration levels can cause significant dangers and problems in surgery, such as a surge of fluid into the cannula after an occlusion of the cannula has been cleared. This post-occlusion surge can cause the collapse of the eye resulting in damage to delicate tissues in the eye and in serious damage to the eye.
Therefore, it would be desirable to provide a phacoemulsification cannula with increased purchase as compared to the prior art without the need to significant increase the aspiration levels applied through the cannula's lumen.